It has been recognized in the operation of such power-producing apparatus as gas turbine engines that friction between rotating and stationary cooperating members can generate metallic particles which can be accumulated or entrapped downstream of the point of friction. Of particular interest has been titanium debris which can result from planned or occasional interference between compressor blades and opposed, cooperating portions of the compressor, rotating relative one to the other. Because of the highly oxidizing, high-velocity, pressure conditions which can exist in a gas turbine engine, titanium debris, once ignited by some unusual occurrence, can burn with high intensity and can, in some cases, penetrate walls of engine casings even though its burning duration is relatively short. If such penetration occurs in the vicinity of fuel or lubrication conduits, penetration of such conduits can occur. This can result in still further spread of the fire, inhibiting its containment and mechanisms to extinguish it.
Further complicating such problems in aircraft gas turbine engines is the proximity of such conduits to casings of the engine and the complex configuration of such conduits in order to provide fuel and lubricant to selected portions of the apparatus. Therefore, a system which is sufficiently fire retardant to avoid penetration of burning metallic particles must be relatively thin in order to be useful in such apparatus.